Climate Change Research at VBG
VBG have been collaborating with Universities including Texas State University, University of Nottingham and University of Leeds. The research has been focussed on morphological characteristics of present day extant plants compared to fossilised plant material from millions of years ago.
For Texas State University we have propagated and supplied live plant material of Cryptocarya alba, a Chilean tree. This tree is rarely seen outside of South America, it needs warm conditions that very few UK gardens can guarantee. The unique microclimate of Ventnor is perfect, so the one at VBG is nearly forty years old and the largest in the UK. National Science Foundation Graduate Research Fellow Jon D. Richey summarises his research below:
Reconstructing Changes in pCO2 across the Albian-Cenomanian Boundary and OAE1d.
Jon D. Richey
The goal of this project is to examine changes in atmospheric CO2 levels during a disturbance in the global carbon cycle at the Albian-Cenomanian Boundary (known as Ocean Anoxic Event 1d, approx. 100 million years ago). This event is similar in some ways to the current release of large amounts of CO2 to the atmosphere due to human activities. Ocean Anoxic Events (OAEs) have been relatively common during hot climates of the geologic past, and, given current climatic trends, are growing concerns.
I am using a botanical method known as Stomatal Index (SI, the percentage of epidermal cells in the leaves of plants that are stomata [gas exchange pores]) to look at variation in CO2 throughout OAE1d. SI varies inversely with CO2 because at high atmospheric CO2 levels, an individual plant can maintain a high level of photosynthesis while minimizing H2O loss by having fewer stomata. Epidermal cells and stomata are counted in modern materials, such as subfossil and herbarium specimens, to calculate SI, which is compared to atmospheric CO2 levels from when they were collected. An equation is generated that describes the relationship from that data.
Modern plants have been exposed to atmospheric CO2 levels between 180 – 280 parts per million for 800,000+ years. Therefore, any equation derived from modern plants is inherently biased to lower CO2 levels. Due to this, growth chamber work, where modern plants are subjected to highly elevated CO2 levels in specially designed growth cabinets, is very important. To do this, I have enlisted the help of Chris Kidd, curator of the Ventnor Botanic Gardens, who has supplied plants of the modern species Cryptocarya alba (Lauraceae). These plants will be subjected to elevated CO2 levels in a growth chamber at the University of Nottingham by my collaborator, Dr. Barry Lomax. This will ensure that the equations derived in this work will have the ability to predict CO2 levels during the warm climate of the Cretaceous.
I have obtained cuticle (the waxy covering of leaves, which are high decay resistant and can be recovered in rock dating back to the first land plants) of members of the fossil genus Pandemophyllum (Lauraceae) from the only sediments currently known to preserve OAE1d. I will calculate SI from this cuticle, which will be plugged into the equation derived from modern material to infer CO2 levels during OAE1d. In addition, I have isolated fossil charcoal from the same sediments that yielded the fossil cuticle used in my study. d13C is the ratio of carbon-12 to carbon-13 and changes due to many factors, such as differences in photosynthesis. In plants that perform C3 photosynthesis, trends in d13C match changes in the atmospheric d13C. The isolated charcoal will be processed to generate a d13C curve. Since the d13C and CO2 data points will be from the same moment during OAE1d, comparison of this data may illuminate possible causes and consequences of carbon release during that event, which will, in turn, provide information about the current anthropogenic carbon release.*
*This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144466. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
For the University of Leeds VBG supplied live plant material of its accessions of Ginkgo biloba, an extant species of a very ancient order of plants originating some 240 million years ago. Karen Bacon summarises her research below:
Testing the plasticity of leaf shape in Ginkgo biloba to temperature
This project is an expansion of a very small-scale (unpublished) study that was conducted in 2011 where Ginkgo biloba leaves from Scotland were found to have leaves that differed significantly in shape to leaves collected in London and Cornwall. The current study aims to test whether a much larger sample set from many more locations in the UK can identify the same response in relation to the temperature gradient observed between Scotland and England. The purpose of this study is to help interpretations of recorded ginkgo leaf shape change in the fossil record. In some cases many species of ginkgoites are recorded over a period of time based on differing leaf shape, but this may be a within-taxon response to a period of climate change. Along with the morphology study, detailed anatomy and plant physiology studies are also underway. This is continuing work attempts to link ginkgo leaf shape and anatomy to plant functional traits, such as photosynthesis. The aim of this is to determine if changes in leaf morphology or cell structure can be linked to changes in plant function, which could then be identified in the fossil record. Ginkgo biloba has been selected for this study due to its long history (over 230 million years) in the fossil record and due to its presence in many locations in the UK. This will hopefully help us to understand how plants responded to previous periods of climate change. The study will be expanded in the coming years to include locations outside of the UK and to include other gymnosperm groups.
Research into Gingko leaf morphology
Frances Procter, University of Leeds
This current research, using leaves of two Ginkgo accessions growing at VBG, sets out to test if there are issues with classification of Ginkgophytes in the fossil record, by investigating the variations within Ginkgophyte leaf morphology. Frances Procter is doing this by collecting large samples of modern day Ginkgo biloba, from different localities and climates across the UK, investigating the leaf morphology between them, and also investigating variations within one tree (i.e. height in the canopy, and exposure to sunlight). Procter has been photographing the leaves to conduct morphometric analyses. The findings will be compared with a large number of fossilised leaves from British museums, assigned to multiple different species.